1. Field of the Invention
The present invention is directed to a method for aligning reflectors subjected to a driving force, and more specifically, for aligning micromachined optical switches.
2. Description of the Related Art
Optical switches are devices that can selectively switch optical signals from one optical circuit to another, and are typically used in optical systems such as optical add/drop multiplexers (OADMs). Various technologies can be used in optical switches, including, but not limited to, physically shifting an optical fiber to drive one or more alternative fibers, physically moving a reflective element, using electro-optic effects, or using magneto-optic effects.
For an optical switch to work effectively, proper alignment of the switch is desirable. In the case of optical switches that operate based on the physical movement of one or more reflective elements subjected to a driving force, misalignment of the reflective elements with respect to the optical signal being switched can cause the optical signal to switch improperly, or to fail to switch entirely. For example, a reflective element designed to move in an intended mechanical mode may also move in an unintended mode if the driving force is applied improperly. Motion of the reflective element in an unintended mode can cause the optical signal leaving the switch to reach only a portion of the detector or fiber receiving the optical signal from the switch, thereby introducing losses into the optical circuit, and causing the optical switch to attenuate the optical signal.
Misalignment of reflective elements in an optical switch may be caused by a variety of factors. In addition to external forces to which the optical switch may be subjected, environmental factors such as extreme temperatures or pressures can cause misalignment. Moreover, misalignment may occur if the reflective elements are subjected to driving forces that physically move the reflective elements in and out of the path of the optical signal. Thus, it is desirable to develop a method for aligning the reflective element of an optical switch so that when a driving force is applied, the reflective element moves in only the intended mode.
According to one aspect of the present invention, a method reduces movement of a reflector in an unintended mechanical mode during movement of the reflector in an intended mechanical mode. The method comprises using a reflector driver to apply a distribution of forces to the reflector so as to move the reflector both in the intended mechanical mode and in the unintended mechanical mode. The distribution of forces is applied at a resonant frequency of the unintended mechanical mode. The method further comprises adjusting the reflector driver to alter the distribution of forces applied to the reflector such that the movement of the reflector in the unintended mechanical mode is reduced.
According to another aspect of the present invention, a device measures a direction of a component of a magnetic field. The device comprises a mechanical system positionable in the magnetic field. The mechanical system comprises a substrate and a flap that is mechanically coupled to the substrate and that has a mechanical resonance mode with a resonance frequency. The mechanical system further comprises a reflector coupled to the flap, and an electrical conduit formed on the flap to allow an electrical current flowing through the electrical conduit to interact with the magnetic field to apply a driving force to the flap. The device further comprises an electrical current source coupled to the electrical conduit. The electrical current source is adapted to generate an electrical current with a time-dependent component with a frequency substantially equal to the resonance frequency. The device further comprises a light source adapted to generate a collimated light beam incident on the reflector, with the reflector reflecting at least a portion of the collimated light beam. The device further comprises a detector adapted to detect a displacement of the reflected portion of the collimated light beam.